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DARPA ULTRALOG Final Report - Industrial and Manufacturing ...

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Manuscript for IEEE TRANSACTIONS ON PARALLEL AND DISTRIBUTED SYSTEMS 8<br />

algorithm selection (v) <strong>and</strong> resource allocation (w) as in (2). As stated earlier, we design a<br />

scalable control mechanism to achieve the objective in the framework of MPC by building a<br />

mathematical programming model <strong>and</strong> decentralizing it.<br />

arg max<br />

v,w<br />

e<br />

i<br />

∑∑<br />

i∈ A d = 1<br />

v<br />

d<br />

i<br />

− CCT(T )<br />

(2)<br />

3. Mathematical programming model<br />

The mathematical programming model is essentially a scheduling problem formulation. There<br />

are a variety of formulations <strong>and</strong> algorithms available for diverse scheduling problems in the<br />

context of multiprocessor, manufacturing, <strong>and</strong> project management. In general, a scheduling<br />

problem is allocating limited resources to a set of tasks to optimize a specific objective. One<br />

widely studied objective is completion time (also called makespan in the manufacturing<br />

literature) as the problem we have considered. Though it is not easy to find a problem exactly<br />

same as ours, it is possible to convert our problem into one of the scheduling problems. For<br />

example, in job shop, there are a set of jobs <strong>and</strong> a set of machines. Each job has a set of serial<br />

operations <strong>and</strong> each operation should be processed on a specific machine. A job shop scheduling<br />

problem is sequencing the operations in each machine by satisfying a set of job precedence<br />

constraints such that the completion time is minimized. When we assign a value mode to each<br />

task, our problem can be exactly transformed into a job shop scheduling problem. However,<br />

scheduling problems are in general intractable. Though the job shop scheduling problem is<br />

polynomially solvable when there are two machines <strong>and</strong> each job has two operations, it becomes<br />

NP-hard on the number of jobs even if the number of machines or operations is more than two<br />

[19][20]. Considering that the task flow structure of our networks is arbitrary, our scheduling

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